In the semiconductor arts “self-alignment” is among known techniques for maintaining lateral alignment of a window as it is etched through an upper layer, for example, to a contact pad in an underlying layer. The technique generally utilizes upper layer circuit features already having the desired alignment as a hard mask to perform the etching. Conventional self-alignment techniques include covering certain upper layer features with silicon nitride (hereinafter “nitride”) or other hard mask material to protect against etching damage. For example, there are conventional techniques for forming nitride caps over certain metal features to utilize them as self-alignment.
Conventional techniques for forming such protection, though, can have costs. For example, in the fabrication of finned field effect transistors (FinFETs), nitride caps can be formed on in-process adjacent metal gates on a common fin. The nitride capped adjacent fins can then assist in a self-aligning etching of a window for a source/drain contact. However, the nitride cap must have a certain thickness for acceptable protection against shorting of gate metal to source/drain contact. Conventional techniques include etching a recess in the gate metal between the gate spacers, as deep as the desired cap thickness, then filing the deep recess with nitride. This can have costs, including increased gate resistance.